The invention relates to an adjustable mount for mirrors used in a laser resonator, and especially to a laser resonator where weight and size are basic constraints and where great stability of the mirror mount is desireable.
In laser resonators as well as other optical reflecting systems, a reflector or mirror may be mounted for angular adjustment. Various devices have been designed to allow accurate and easy adjustment of the angular position of optical elements for use with lasers. The following U.S. patents are cited as examples of the various types of mirror mounts: U.S. Pat. No. 3,478,608 to V. Met; U.S. Pat. No. 3,601,476 to D. R. MacKenzie; U.S. Pat. No. 3,700,313 to Karr et al.; U.S. Pat. No. 3,836,236 to Kirk et al.; U.S. Pat. No. 3,783,407 to Mefferd et al.; U.S. Pat. No. 3,953,113 to W. A. Shull; and U.S. Pat. No. 4,274,064 to Sepp, et al. In prior U.S. Pat. No. 4,268,799 a curved mirror laser is utilized along with a method of operating the laser.
These prior devices as well as others are designed to solve the problems associated with the assembly of a laser or its operation during changes of temperature of the laser components. However, there are problems associated with lasers used in conditions of high vibration surroundings and the ability of the resonator mount to withstand high acceleration or shock and still retain its alignment. The present invention is designed for use under these conditions.
U.S. Pat. No. 3,924,201 discloses a cross porro resonator which provides a solution to the above-stated problem and hence the approach is briefly described herein. The porro prism acts as a retroreflector which is sensitive to tilt about an axis perpendicular to the roof edge within the limits imposed by total internal reflection. The cross porro resonator requires a polarizer for output coupling. For a stable system the axis of the system must pass through the apex of each prism. The angular alignment tolerance possible with the said resonator can be given by: ##EQU1## where D is the laser rod diameter
.theta. is angle between porro roof edges and PA1 L is the resonator length.
Thus, for a laser rod of diamater D=0.63 cm and a cross porro prism angle .phi.=90.degree., and an angle .theta. (for resonator length L=50 cm) of 6.3 mR or 0.36 degrees. An angle of misalignment higher than 0.36 l degrees degrades the performance of the laser resonator so that the resonator is considered less sensitive to vibration and shock environments and is mechanically stable. However, the cross porro resonator requires a polarizer to extract the output, along with waveplates to adjust the output coupling reflectivity. These components also require stable mounts and this increases the size and weight of the resonator. The laser resonator mirror mounting means of the present invention accomplishes improved mechanical stability in a sample configuration.